bjoernager/rust
bjoernager/rust
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This commit is contained in:
Michael Goulet 2023-07-30 21:46:04 +00:00
parent ca49a37390
commit 0e20155662
5 changed files with 65 additions and 49 deletions
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33
compiler/rustc_trait_selection/src/traits/select/mod.rs
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@ -202,10 +202,25 @@ enum BuiltinImplConditions<'tcx> {
#[derive(Copy, Clone)]
pub enum TreatInductiveCycleAs {
/// This is the previous behavior, where `Recur` represents an inductive
/// cycle that is known not to hold. This is not forwards-compatible with
/// coinduction, and will be deprecated. This is the default behavior
/// of the old trait solver due to back-compat reasons.
Recur,
/// This is the behavior of the new trait solver, where inductive cycles
/// are treated as ambiguous and possibly holding.
Ambig,
}
impl From<TreatInductiveCycleAs> for EvaluationResult {
fn from(treat: TreatInductiveCycleAs) -> EvaluationResult {
match treat {
TreatInductiveCycleAs::Ambig => EvaluatedToUnknown,
TreatInductiveCycleAs::Recur => EvaluatedToRecur,
}
}
}
impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
pub fn new(infcx: &'cx InferCtxt<'tcx>) -> SelectionContext<'cx, 'tcx> {
SelectionContext {
@ -223,6 +238,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
treat_inductive_cycle: TreatInductiveCycleAs,
f: impl FnOnce(&mut Self) -> T,
) -> T {
// Should be executed in a context where caching is disabled,
// otherwise the cache is poisoned with the temporary result.
assert!(self.is_intercrate());
let treat_inductive_cycle =
std::mem::replace(&mut self.treat_inductive_cycle, treat_inductive_cycle);
let value = f(self);
@ -741,10 +759,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
stack.update_reached_depth(stack_arg.1);
return Ok(EvaluatedToOk);
} else {
match self.treat_inductive_cycle {
TreatInductiveCycleAs::Ambig => return Ok(EvaluatedToUnknown),
TreatInductiveCycleAs::Recur => return Ok(EvaluatedToRecur),
}
return Ok(self.treat_inductive_cycle.into());
}
}
return Ok(EvaluatedToOk);
@ -862,10 +877,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
}
}
ProjectAndUnifyResult::FailedNormalization => Ok(EvaluatedToAmbig),
ProjectAndUnifyResult::Recursive => match self.treat_inductive_cycle {
TreatInductiveCycleAs::Ambig => return Ok(EvaluatedToUnknown),
TreatInductiveCycleAs::Recur => return Ok(EvaluatedToRecur),
},
ProjectAndUnifyResult::Recursive => Ok(self.treat_inductive_cycle.into()),
ProjectAndUnifyResult::MismatchedProjectionTypes(_) => Ok(EvaluatedToErr),
}
}
@ -1179,10 +1191,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
Some(EvaluatedToOk)
} else {
debug!("evaluate_stack --> recursive, inductive");
match self.treat_inductive_cycle {
TreatInductiveCycleAs::Ambig => Some(EvaluatedToUnknown),
TreatInductiveCycleAs::Recur => Some(EvaluatedToRecur),
}
Some(self.treat_inductive_cycle.into())
}
} else {
None